1. Field of the Invention
The present invention relates to an electromagnetic compressor and a manufacturing method therefor, and more particularly, to an electromagnetic compressor suitably used to suck in and compress a combustible gas, such as town gas, or some other gas and a manufacturing method therefor.
2. Description of the Related Art
Conventionally, electromagnetic compressors that compress and discharge fluids such as air have widely been used, and various inventions related to the electromagnetic compressors have been made. A typical example of an electromagnetic compressor of this type is described in Jpn. Pat. Appln. KOKOKU Publication No. 57-30984, which will be described in brief with reference to FIG. 13.
An electromagnetic compressor 200 has a structure such that a front frame 202 and a front cover 203 are arranged successively in front (see the left-hand side of the drawing) of a stationary electromagnetic circuit 201, while a rear frame 204 and a rear cover 205 are arranged successively in the rear (see the right-hand side of the drawing). These elements are coupled together to form the body shell of the electromagnetic compressor 200.
The front frame 202 has a front collar 206 and a rear collar 207. The front collar 206 is formed integrally having a front fitting cylinder portion 208 and a rear fitting cylinder portion 209 that are aligned with each other. A front cylinder 210 is fitted in the front fitting cylinder portion 208, a rear cylinder 211 is fitted in the rear fitting cylinder portion 209, and the front frame 202 and the rear cylinder 211 are fixed together by means of a plurality of screws 212.
The rear frame 204 has a front collar 213 and an outer collar 214. The rear collar 207 of the front frame 202 and the front collar 213 of the rear frame 204 are screwed together to the stationary electromagnetic circuit 201. Thus, the respective opposite faces of the rear collar 207 and the front collar 213 abut against the front and rear faces, respectively, of the stationary electromagnetic circuit 201.
The stationary electromagnetic circuit 201 is wound with a coil 215. North or south magnetic poles that are formed as the coil 215 is energized are located in longitudinal notches of the rear fitting cylinder portion 209. A magnetic armature 220 that is electromagnetically attracted to the magnetic poles is held between a front piston 222, which has a piston head 221 slidable in the front cylinder 210, and a rear piston 223 slidable in the rear cylinder 211. These three elements are fixed together by means of a screw 224. A return spring 226 is interposed between the rear piston 223 and a cap 225 of the rear cylinder 211.
If the stationary electromagnetic circuit 201 is excited in the compressor constructed in this manner, the magnetic armature 220, which is integral with the front and rear pistons 222 and 223 (hereinafter referred to simply as the piston 222), is advanced by electromagnetic attraction as illustrated, resisting the resilient force of the return spring 226. If the excitation is cancelled, on the other hand, the piston 222 returns pressed by the return spring 226. As the piston 222 reciprocates in this manner, air in a working chamber 227 that is fixed in the front cylinder 210 is repeatedly brought to rare and dense states.
Thus, when the piston 222 is retreated by means of the force of electromagnetic attraction, an inlet valve 228 attached to the piston head 221 opens to the working chamber 227. Thereupon, air introduced into the compressor body through inlet ports 230 of the rear cover 205 flows into the working chamber 227 through a filter 231, supply holes 232, 232, and inlet ports 233. When the piston 222 advances pressed by the return spring 226, on the other hand, the air in the working chamber 227 becomes dense. Consequently, a discharge valve that is attached to a part of the wall portion of the working chamber 227 opens, whereupon the compressed air is supplied through discharge ports 234, a tank 235, and a discharge port 236 to an external apparatus that is connected to a hose as required.
If the compressor constructed in this manner is applied to the suction and compression of a combustible gas such as town gas, however, the combustible gas sucked into the working chamber 227 is inevitably guided to the supply holes 232 and the inlet ports 233 via the periphery of electrical parts, e.g., the coil 215 and the like. Since the front and rear faces of the stationary electromagnetic circuit 201, the rear collar 207, and the front collar 213 abut against one another, moreover, there is a possibility of the combustible gas leaking out through the abutting portions.
According to the present invention, there is provided an electromagnetic compressor capable of reciprocating a piston to suck in and compress a gas by means of the force of attraction of an electromagnet and the resilient force of a return spring. The compressor comprises a cylinder assembly including a front cylinder portion, a rear cylinder portion, and a center hole capable of storing the piston for reciprocation and having a working chamber defined by the piston; an electromagnet located between the front cylinder portion and the rear cylinder portion and capable of actuating the piston; an electrically conductive member for supplying electricity to the electromagnet; and an internal passage connecting the working chamber to the outside of the compressor. The cylinder assembly and the electromagnet have an integral structure molded from a resin in a manner such that the internal passage is hermetically sealed with respect to the electromagnet and the electrically conductive member.
According to the present invention, there is further provided an electromagnetic compressor capable of reciprocating a piston to suck in and compress a gas by means of the force of attraction of an electromagnet and the resilient force of a return spring. The compressor comprises a housing assembly having a center hole in which the piston is located and a resin layer molded around an electromagnet forming a pair of magnetic poles on the diametrically opposite sides of the piston; and a cylinder portion stored in the center hole, storing the piston for reciprocation, and having a working chamber defined by means of the piston. The inside diameter of the cylinder portion and the outside diameter of the piston sliding in the cylinder are selectable.
According to the present invention, there is still further provided a manufacturing method for an electromagnetic compressor capable of reciprocating a piston to suck in and compress a gas by means of the force of attraction of an electromagnet and the resilient force of a return spring. The method comprises providing a cavity-side mold having a cavity and a columnar protrusion for centering in the cavity and a movable mold having a gate hole; inserting an iron core wound with coils along the columnar protrusion into the cavity-side mold and positioning the iron core so that magnetic poles formed on the iron core are located in given positions; locating the movable mold on the cavity-side mold; and injecting a thermosetting resin into the molds through the gate hole of the movable mold, thereby molding a housing assembly.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.